Composition for forming metal oxide thin film pattern and method for forming metal oxide thin film pattern

ABSTRACT

A composition for forming a metal oxide thin film pattern which is a solution containing one or more hydrolytic metal compounds selected from the group consisting of hydrolytic organometallic compounds (e.g., metal alkoxide) and metal halides, and a water generating agent which frees water under the effect of irradiation with active rays (e.g., o-nitrobenzyl alcohol and 2-nitroethanol) and, as required, an acid generating agent which frees acid under the effect of irradiation with active rays is disclosed. A thin film pattern is formed by coating the composition onto a substrate, irradiating active rays for forming an image on the resultant photosensitive coating film, developing the same with water or an alcoholic solvent to remove the non-exposed portion, and heat-treating the substrate to convert the remaining film into a metal oxide, thereby forming a negative-type metal oxide thin film pattern.

FIELD OF THE INVENTION

The present invention relates to a composition for forming a metal oxidethin film pattern, which is sensitive to active rays such as ultravioletrays, an electron beam, an ion beam or X-rays, and a method for forminga metal oxide thin film pattern by means thereof.

DESCRIPTION OF THE RELATED ART

A metal oxide thin film is used in various devices in the form of acapacitor film, an optical wave guide and an optical element because ofits electrical and optical properties. When using a metal oxide thinfilm in such a device, it is usually necessary to form a thin filmpattern so as to form a prescribed circuit.

A metal oxide thin film pattern has conventionally been formed, afterforming a metal oxide thin film on a substrate by any of a CVD method,sputtering method, and sol-gel method, through an ordinary resistpatterning process comprising the steps of (1) applying a resist, (2)drying, as required, the resist by heating, (3) exposing the driedresist to radiation to form an image, (4) developing the exposed resist,(5) etching the metal oxide on the exposed portion, and (6) removing theresist.

The conventional thin film patterning method using the resist has thefollowing problems:

(a) the process is complicated, resulting in a high cost;

(b) when the thin film is of composite metal oxides, specific elementsare preferentially etched causing a shift in the resultant thin filmcomposition; and

(c) waste treatment of a liquid such as a strong acid used for etchingthe metal oxide is troublesome.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a composition whichpermits formation of a metal oxide thin film pattern on a substrate anda method for forming a metal oxide thin film pattern, without using aresist.

Another object of the present invention is to provide a composition forforming a metal oxide thin film pattern, which permits formation of athin film pattern by irradiation with active rays of energy of a slightamount, and a method for forming same.

The composition for forming a metal oxide thin film pattern of the firstaspect of the present invention comprises a solution containing one ormore hydrolytic metal compounds selected from the group consisting ofhydrolytic organometallic compounds and metal halides, and aphotosensitizer which forms water when irradiated with active rays.

The method for forming a metal oxide thin film pattern of the secondaspect of the present invention comprises the steps of applying thecomposition of the first aspect onto a substrate, exposing the resultantfilm to active rays to form an image, developing the same with a solventto remove a non-exposed portion, and then subjecting the same to a heattreatment to convert the exposed film portion into a metal oxide.

The composition for forming a metal oxide thin film pattern of the thirdaspect of the present invention comprises a solution containinghydrolytic metal compounds and one or more compounds selected from thegroup consisting of 2-nitroethanol, formaldehyde, tartaric acid,2-hydroxybenzyl alcohol, 2-carboxybenzyl alcohol, 2-carboxybenzaldehyde,2-nitrobenzaldehyde, and phthalic acid.

The method for forming a metal oxide thin film pattern of the fourthaspect of the present invention comprises the steps of applying thecomposition of the third aspect as described above onto a substrate,exposing the resultant film to active rays to form an image, developingthe same with a solvent to remove a non-exposed portion, and thensubjecting the same to a heat treatment to convert the exposed filmportion into a metal oxide.

The present inventors previously proposed the possibility of forming anegative type metal oxide pattern without using a resist on the basis ofthe discovery that a coated film of a solution containing a metalalkoxide and a metal carboxylate, used for forming a metal oxide thinfilm by the sol-gel method, had sensitivity to radiation, and byutilization of this sensitivity, only a non-exposed portion could beremoved by irradiating the coated film of the above-mentioned solutionto harden the exposed portion thus irradiated (Japanese Laid Open PatentPublication No. 6-172,068).

Further studies relating to this method gave the following findings. Bymodifying the composition to contain a photosensitizer which forms waterunder the effect of irradiation, water produced at an exposed portionaccelerates polymerization through hydrolysis at the exposed portion. Asa result, it is possible to make a large difference in solubilitybetween exposed and non-exposed portions with a smaller amount ofirradiated energy, thus making it easier to remove the non-exposedportion. As this photosensitizer, specific compounds exhibit excellentproperties. Furthermore, by adding a photosensitizer which separates anacid under the effect of irradiation to the composition, an acidproduced at the exposed portion further accelerates the hardeningreaction, thus permitting a larger exposed portion to be obtained. Thepresent inventors have thus developed the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is described below in further detail.

Hydrolytic metal compounds useful in the present invention includehydrolytic organometallic compounds and metal halides.

There is no particular limitation as to the hydrolytic organometalliccompounds as long as a metal hydroxide can be formed from the compoundthrough hydrolysis. Typical examples include metal alkoxides, metalacetylacetonate complexes and metal carboxylates. A preferred metalalkoxide is a lower alkoxide such as an ethoxide, propoxide,isopropoxide, butoxide or isobutoxide. Similarly, a preferred metalcarboxylate is a metal compound of a lower aliphatic acid such as anacetate or propionate.

As the metal halide, a chloride can be used.

For each metal element, one or more hydrolytic metal compounds can beused as a raw material.

There is no particular limitation regarding the metal in the hydrolyticmetal compounds, but it is preferred to select a hydrolytic metalcompound corresponding to the thin film of the applied metal oxide (twoor more metal elements in the case of composite oxides).

The composition and the method of the present invention are suitable forthe formation of a thin film pattern of metal oxides (including bothcomposite metal oxides and single metal oxides) such as lead titanatezirconate (PZT), lanthanum-containing lead titanate zirconate (PLZT),strontium titanate (STO), barium titanate (BTO), barium-strontiumtitanate (BSTO), bismuth titanate (Bi₄ Ti₃ O₁₂), tantalum oxide (Ta₂O₅), titanium dioxide (TiO₂), lead oxide (PbO), zirconium dioxide(ZrO₂), alumina (Al₂ O₃), tin dioxide (SnO₂), and ruthenium dioxide(RuO₂). To form thin films of these metal oxides, hydrolyticorganometallic compounds and/or metal halides of the metals of thesemetal oxides are employed.

The composition of the present invention can contain only one or both ofa hydrolytic organometallic compound and a metal halide.

The composition of the present invention contains, together with theabove-mentioned hydrolytic metal compound, a photosensitizer whichreleases water by irradiation of active rays (hereinafter referred to as"water generating agent") for the following reasons.

The hydrolytic metal compound used in the present invention is subjectedto hydrolysis through reaction with water, and transforms into a gelthrough a sol of a water-containing metal oxide. As the reactionproceeds further, a polymerization reaction takes place, wherein acombination of the metal and oxygen achieves a three-dimensional bridge,resulting in hardening of the film.

As described above, the hydrolytic metal compound is sensitive to theradiation. Upon irradiation, the polymerization reaction preferentiallytakes place in the exposed portion, and as a result, the film thereinbecomes denser and harder. This produces a difference in solubilitybetween the exposed and the non-exposed portions, and by the utilizationof this phenomenon, it is possible to form a pattern.

By previously adding the water generating agent, together with thehydrolytic metal compound as described above, to form the composition,water released from the water generating agent by the irradiation withthe active rays can accelerate considerably the hardening reaction ofthe above-mentioned hydrolytic metal compound. In other words, watergenerated by the water generating agent serves as a kind of hardeningcatalyst. In the portion exposed to the active rays, therefore, thehardening reaction of the film proceeds to a considerable extent, and ascompared with a case without the addition of the water generating agent,the difference in solubility between the exposed and the non-exposedportions becomes considerably large. Since the water generating agenthas a higher sensitivity to active rays than the hydrolytic metalcompound itself, the above-mentioned hardening reaction can be startedand promoted with a smaller amount of active ray energy.

As the water generating agent, any compound capable of forming waterthrough a dehydration reaction which takes place within or betweenmolecules by irradiation with active rays can be used. Useful compoundsinclude an aromatic organic compound having an active ray sensitivityand containing electron attractive groups such as a nitro group andelectron donative groups such as a hydroxyl group within a molecule. Theelectron attractive group and the electron donative group shouldpreferably be present in relatively close proximity to each other.Examples of such compounds include O-nitrobenzyl alcohol, and1-hydroxymethyl-2-nitronaphthalene. In the case of O-nitrobenzylalcohol, for example, dehydration occurs within a molecule through thereaction:

    C.sub.6 H.sub.4 (CH.sub.2 OH)NO.sub.2 →C.sub.6 H.sub.4 (CHO)NO+H.sub.2 O

and water is generated.

In the third aspect of the present invention, one or more compoundsselected from the group consisting of 2-nitroethanol, formaldehyde,tartaric acid, 2-hydroxybenzyl alcohol, 2-carboxybenzyl alcohol,2-carboxybenzaldehyde, 2-nitrobenzaldehyde and phthalic acid are usedspecifically as the water generating agent. These water generatingagents, when irradiated with active rays, undergo a dehydration reactionto generate water.

In the composition of the present invention, a photosensitizer whichfrees acid by irradiation of active rays (hereinafter referred to as"acid generating agent") can be used simultaneously with the watergenerating agent, with a view to further accelerating the hydrolysisreaction of the hydrolytic metal compound by the water generating agent.In the presence of the acid generating agent, acid generated byirradiation with active rays on the exposed portion acts as a catalystfor the hardening reaction of the hydrolytic metal compound to furtherpromote hardening, thus further increasing the difference in solubilitybetween the exposed and the non-exposed portions and enabling the amountof irradiation to be further reduced.

As the acid generating agent capable of being used simultaneously withthe water generating agent in the present invention, any of thosecompounds conventionally known in the area of photoresist can be used.Applicable acid generating agents include:

(1) onium salts such as an iodonium salt and sulfonium salt;

(2) organic halides such as an halogen-containing benzene derivative, anhalogen-containing alkane or cycloalkane, and an halogen-containings-triazine or isocyanurate derivative;

(3) o- or p-nitrobenzylester; and

(4) an aromatic sulfonic ester or sulfonyl compound such as a benzenepolysulfonic ester, bisallylsulfonyl diazomethane, and2-phenylsulfonylacetophenone.

One or more kinds of both the water generating agents and the acidgenerating agents can be used.

The composition for forming a metal oxide thin film pattern of thepresent invention can be prepared by dissolving a raw materialhydrolytic metal compound in an appropriate organic solvent (e.g.,ethanol, isopropanol, 2-methoxyethanol or other alcohol; acetic acid,propionic acid or other lower aliphatic carboxylic acids), adding awater generating agent (or a water generating agent and an acidgenerating agent) to the resultant solution, and causing dissolutionthereof. When the object is a composite oxide thin film pattern, two ormore raw material hydrolytic metal compounds are used in a ratiocorresponding to the ratio of the individual metals in the compositeoxide.

The concentration of the hydrolytic metal compound or compounds in thecomposition should preferably be within a range of from 1 to 20 wt. %.The quantity of water generating agent should be within a range of from0.001 to 20 wt. %, or more preferably, from 0.1 to 10 wt. %, relative tothe total weight of the composition.

A quantity of added water generating agent smaller than the prescribedrange cannot bring about a large difference in solubility between theexposed and the non-exposed portions, thus making it impossible to forma clear pattern. With a quantity of added water generating agent largerthan the prescribed range, irradiation causes denaturation of the coatedfilm of even the surrounding non-exposed portion, thus also making itimpossible to form a clear pattern. When simultaneously adding the acidgenerating agent, the quantity thereof should be within a range of from0.001 to 20 wt. %, or more preferably, from 0.1 to 10 wt. %, relative tothe total weight of the composition. In this case, the sum of thequantities of the water generating agent and the acid generating agentshould preferably be up to 20 wt. % of the total weight of thecomposition.

A chelating compound such as acetylacetone, ethanolamine and ethyloxo-butanoic acid can be added as a stabilizing agent which preventsgelation during storage. The chelating compound is added in an amount offrom 0.05 to 10 mol relative to 1 mol of the hydrolytic metal compoundin the resultant solution.

While there is no particular limitation on the method for applying thiscomposition to the substrate so far as it permits formation of a filmhaving a uniform thickness, a spin-coat method is commonly adopted forindustrial purposes. As required, a desired film thickness can beobtained by repeating the application operation after gelation of thefilm. It is also possible to increase the film thickness of the metaloxide thin film in the present invention, since irradiation is possiblewith a smaller amount of energy through addition of the water generatingagent. The metal oxide thin film formed with the composition of thepresent invention should preferably have a thickness (in general) withina range of from 0.01 to 0.2 μm.

The resultant film loses its fluidity if held for a short period oftime, and permits exposure. The holding time can be set so as to dry thefilm (i.e., so as to cause the film to lose its fluidity) to the extentof permitting irradiation with active rays for forming an image, and isusually within a range of from several seconds to several minutes.

Then, the film is exposed for image formation by irradiation with activerays to form an image corresponding to a desired pattern. Applicableactive rays vary with the adopted photosensitizer (water generatingagent and acid generating agent) and generally include ultraviolet rays,an electron beam, an ion beam and X-rays. The source of ultraviolet rayscan be, for example, a low-voltage mercury lamp, or an excimer laser.The image-forming exposure can be conducted by irradiating the activerays through a mask by a conventional method, or when the active-raysource is a laser, by a direct drawing method consisting of irradiatinga patterned laser beam. The amount of energy of irradiation is notspecifically limited, but an amount of at least 100 mJ/cm² suffices,varying however with the film thickness and the kind of thephotosensitizer.

As a result of irradiation with the active rays, the hardening reaction,the hydrolysis reaction and the polymerization reaction of theabove-mentioned coated film proceed in the exposed portion, and thecoated film becomes harder and denser, so that solubility thereof in asolvent such as an alcohol decreases. In the present invention in whichthe water generating agent is present, the hardening reaction of theexposed portion can be selectively promoted with a smaller amount ofirradiation energy of the active rays. The objective of irradiation canbe sufficiently achieved, not only with rays having a very high energydensity such as an electron beam, but also with ultraviolet rays havingan energy density lower than this. In the simultaneous presence of theacid generating agent in the film, acid generated in the exposed portionfurther accelerates the hardening reaction of the film.

As required, the film can be held, after irradiation, in a dry inert gas(such as nitrogen or argon) atmosphere at 40° to 100° C. for one to tenminutes. By thus maintaining the temperature while shutting the film offfrom moisture in the air, it is possible to further promote selectivelythe hardening reaction of the film of the exposed portion, thus furtherincreasing the difference in solubility between the exposed and thenon-exposed portions.

After irradiation, the film can be dried, as required, by fully heatingthe substrate. This eliminates moisture and organic solvent remaining inthe exposed portion which forms the target pattern. It suffices toperform this full heating, for example, at 100° to 150° C. for aboutfive to ten minutes.

Thereafter, a negative-type pattern comprising the exposed portion isformed on the substrate by removing the non-hardening film portion onthe non-exposed portion through development by means of an appropriatesolvent. Any solvent which can dissolve the material of the non-exposedportion and has a small solubility against the hardened film of theexposed portion can be used as the developing agent. Use of water or analcohol is preferable. Suitable alcohols include alkoxyalcohols such as2-methoxyethanol and 2-ethoxyethanol. When this type of alcohol is sohigh in solubility as to cause dissolution of the exposed portion,solubility can be adjusted by adding an alkyl alcohol such as ethylalcohol or isopropyl alcohol (IPA). It is not, therefore, necessary touse a strong corrosive acid such as mixed fluoric/hydrochloric acid fordevelopment, and the possibility of accomplishing development with asafe and inexpensive solvent without corrosive action such as an alcoholis one of the important advantages of the present invention.

Development can be conducted, for example, by immersing the film in thesolvent at room temperature for about ten seconds to ten minutes.Conditions of development are set so that the non-exposed portion iscompletely eliminated and the exposed portion is not substantiallyremoved. The conditions of development vary, therefore, with the amountof irradiated active rays, use of a heat treatment, and the kind ofsolvent used for development.

With a view to preventing dissolution of the film in excess of thenecessary level after removal of the non-exposed portion in thedevelopment step, it is desirable to perform rinsing with an appropriateorganic solvent having no or only a very slight solubility for the filmin the exposed portion. For example, esters (e.g., ethyl acetate),ketones (e.g., methyl ethyl ketone, methyl isobutyl ketone), andhydrocarbons (e.g., toluene, n-hexane) are useful as the rinsing liquid.An alcohol having a relatively low polarity such as isopropyl alcoholcan also be used as the rinsing liquid.

A negative-type film pattern comprising the remaining exposed portion isformed on the substrate, Thereafter, a thin film pattern comprising ametal oxide of a desired composition is formed by converting the metalcompounds in the film fully into metal oxides through heat treatment ofthe substrate. This heat treatment should preferably be carried outthrough sintering in an open air atmosphere at 300° to 800° C. for onesecond to two hours.

Another metal oxide thin film pattern of a different kind or of the samekind can be laminated by the same method on the thus formed metal oxidethin film pattern.

In the method of the present invention, the film of the composition ofthe invention is thus formed, and after image-forming exposure, thenon-exposed portion is eliminated through contact with a solvent.Thereafter, the product of the exposed portion is converted to a thinfilm of metal oxides by heat treatment.

When using a compound having a property of being polymerized by activerays as the hydrolytic organic metal compound, a polymerization reactionproceeds in parallel with the above-mentioned hydrolysis reaction, andthis also serves to reduce solubility against a solvent (as comparedwith the absence of irradiation).

Now, the present invention is described in further detail by means ofexamples. The present invention is not limited, of course, to theseexamples. A photo-mask having a line-and-space width of 10 μm (lines,each having a width of 10 μm, arranged at intervals of 10 μm) was usedin the examples.

Metal oxide thin film patterns formed in the Examples were evaluated bymeasuring the line width of the thin film pattern through microscopicobservation. When the thus measured line width (average over tenmeasuring points) was within ±5% of the line width of the mask pattern,the formed thin film pattern was marked good, and a case where there wasa film defect of over 5% was marked poor.

EXAMPLE 1

This experiment presents an example of a negative-type PZT thin filmpattern having a composition:

    PbZr.sub.0.52 Ti.sub.0.48 O.sub.3.

Lead acetate [Pb(CH₃ COO)₂.3H₂ O] in an amount of 11.84 g was dissolvedin 70 g of 2-methoxyethanol, and the resultant solution was heated to140° C. for sufficient dehydration. Commercially available zirconiumn-butoxide [Zr(O(CH₂)₃ CH₃)₄ ] in an amount of 6.87 g and titaniumisopropoxide [Ti(OCH(CH₃)₂)₄ ] in an amount of 4.09 g were added to thissolution. The solution was then diluted with 2-methoxyethanol so as toachieve a total weight of 100 g, and o-nitrobenzyl alcohol (C₆ H₄NO₂.CH₂ OH) in an amount of 2 g was added as a water generating agent.In the thus prepared composition for forming a metal oxide thin filmpattern (hereinafter referred to as a "coating solution"), theindividual metals had an atomic ratio of Pb:Zr:Ti=1:0.52:0.48.

This coating solution was applied by a spin-coat method onto a platinumsubstrate under conditions of 3,000 rpm for 15 seconds to manufacture acoated film. After leaving this coated film at room temperature for oneminute, far-ultraviolet rays (central wavelength: 254 nm) from alow-voltage mercury lamp were irradiated through a mask pattern onto thecoated film. The amount of irradiation was 900 mJ/cm², and a photo-maskof a line-and-space width of 10 μm (10 μm-wide lines were arranged atintervals of 10 μm) was employed. After irradiation of the ultravioletrays, the substrate was dried by heating in a dryer at 100° C. for oneminute. Then, for development, the substrate was immersed in an etchingsolution (2-methoxyethanol) at room temperature for one minute tocompletely dissolve and remove the non-exposed portion of the film.Then, the substrate was immersed in a rinsing solution IPA (isopropylalcohol) at room temperature for five seconds. Subsequently, the filmwas sintered in an open air atmosphere at 400° C. for ten minutes, andfurther in an open air atmosphere at 600° C. for 60 minutes to form anegative-type thin film pattern of PZT having a thickness of about 600Å.

The resultant PZT thin film was confirmed, through X-ray diffraction, tohave a perovskite structure, and through EPMA and XPS analyses, to havea composition PbZr₀.52 Ti₀.48 O₃. A satisfactory thin film pattern wasobtained.

A similar result was available also in a case where a KrF excimer lasergenerating a single wavelength of 249 nm as an ultraviolet ray sourcewas irradiated in the same quantity. In this example, a goodnegative-type PZT thin film pattern could be formed with a quantity ofirradiated ultraviolet rays of at least 100 mJ/cm² (or more preferably,at least 500 mJ/cm²).

Even when the solvent used for development was replaced with a mixedsolution of 2-methoxyethanol and IPA (mixing ratio in volume: 1:1), asimilar satisfactory negative-type pattern was obtained.

EXAMPLE 2

The same steps as in Example 1 were repeated, except that ultravioletrays were irradiated in a quantity of 500 mJ/cm², and, after theirradiation, the substrate was heated in a dried nitrogen atmosphere at50° C. for one minute, and then drying was carried out in a dryer.Development and sintering conditions were the same as in Example 1. Asatisfactory perovskite-type PZT thin film pattern was formed as inExample 1.

Comparative Example 1

Formation of a PZT thin film pattern was attempted as in Example 1,except that o-nitrobenzyl alcohol as a water generating agent was notadded to the composition. There was almost no difference in solubilitybetween the exposed and the non-exposed portions after irradiation withultraviolet rays, and after heating for the purpose of drying,development with water or 2-methoxyethanol or a mixed solvent of2-methoxyethanol and IPA could not selectively eliminate the non-exposedportion.

EXAMPLES 3 TO 16

Solutions comprising the hydrolytic raw material metal compounds andsolvents shown in Table 1 were prepared in the same manner as in Example1, and a coating solution for forming an oxide thin film having a targetcomposition was prepared by adding thereto o-nitrobenzyl alcohol as awater generating agent in an amount of 2 wt. % relative to the weight ofthe solution. A metal oxide thin film pattern was formed by means ofeach of these coating solutions in the same manner as in Example 1. Thecoating thickness was about 600 Å in all cases. Development wasperformed with the use of a mixed solvent of 2-methoxyethanol and IPAand rinsing was performed with the use of n-hexane. In all cases, asatisfactory negative-type thin film pattern comprising a metal oxidehaving a composition as shown in Table 1 could be obtained aftersintering.

                                      TABLE 1                                     __________________________________________________________________________                       Composition for forming metal oxide thin film                                                                    Concentration as        Example                                                                            Composition of metal                                                                        Hydrolytic raw material            converted into          No.  oxide thin film                                                                             metal compound           Solvent   metal oxide             __________________________________________________________________________                                                          (%)                     3    PbTiO.sub.3   Pb(OCOCH.sub.3).sub.2, Ti(OCH(CH.sub.3).sub.2).sub.4                                                   2-methoxyethanol                                                                        10                      4    Pb.sub.0.91 La.sub.0.09 Zr.sub.0.65 Ti.sub.0.35 O.sub.3                                     Pb(OCOCH.sub.3).sub.2, La(OCOCH.sub.3).sub.3,                                                          2-methoxyethanol                                                                        10                                         Zr(O(CH.sub.2).sub.3 CH.sub.3).sub.4,                                         Ti(OCH(CH.sub.3).sub.2).sub.4                              5    Pb.sub.0.8 La.sub.0.2 TiO.sub.3                                                             Pb(OCOCH.sub.3).sub.2, La(OCOCH.sub.3).sub.3,                                 Ti(OCH(CH.sub.3).sub.2).sub.4                                                                          2-methoxyethanol                                                                        10                      6    SrTiO.sub.3   Sr(OCH.sub.2 CH.sub.3).sub.2, Ti(OCH(CH.sub.3).sub.2).s                       ub.4                     2-methoxyethanal                                                                        5                       7    Ba.sub.0.5 Sr.sub.0.5 TiO.sub.3                                                             Ba(OCH.sub.2 CH.sub.3).sub.2, Sr(OCH.sub.2 CH.sub.3).su                       b.2,                     2-methoxyethanol                                                                        5                                          Ti(OCH(CH.sub.3).sub.2).sub.4                              8    PbMg.sub.0.33 Nb.sub.0.67 O.sub.3                                                           Pb(OCOCH.sub.3).sub.2, Mg(OCH.sub.2 CH.sub.3).sub.2,                          Nb(OCH.sub.2 CH.sub.3).sub.5                                                                           2-methoxyethanal                                                                        10                      9    Bi.sub.4 Ti.sub.3 O.sub.12                                                                  BiO(OCOCH.sub.3), Ti(OCH(CH.sub.3).sub.2).sub.4                                                        Acetic acid                                                                             5                       10   ZnO--Al       Zn(OCH.sub.2 CH.sub.3).sub.2, Al(OCH(CH.sub.3).sub.2).s                       ub.3                     2-methoxyethanol                                                                        5                       11   SnO.sub.2 --Sb                                                                              Sn(OC(CH.sub.3).sub.3).sub.4, Sb(O(CH.sub.2).sub.3                            CH.sub.3).sub.5          n-butanol 6                       12   In.sub.2 O.sub.3 --Sn                                                                       In(OCH.sub.2 CH.sub.3).sub.3, Sn(OC(CH.sub.3).sub.3).su                       b.4                      n-butanol 5                       13   TiO.sub.2     Ti(OCH(CH.sub.3).sub.2).sub.4                                                                          2-methoxyethanol                                                                        5                       14   SiO.sub.2     Si(OCH.sub.2 CH.sub.3).sub.4                                                                           Isopropyl alcohol                                                                       5                       15   RuO.sub.2     RuCl.sub.4               Ethanol   5                       16   LiNbO.sub.3   Li(OCH.sub.2 CH.sub.3), Nb(OCH.sub.2 CH.sub.3).sub.5                                                   Ethanol   5                       __________________________________________________________________________

EXAMPLE 17

[Pb(CH₃ COO)₂.3H₂ O] in an amount of 11.84 g was dissolved in2-methoxyethanol serving as the solvent, and the mixture was heated fordehydration. [Zr(O(CH₂)₃ CH₃)₄ ] in an amount of 6.87 g and[Ti(OCH(CH₃)₂)₄ ] in an amount of 4.09 g were added to the mixture, andthe resultant solution was diluted with 2-methoxyethanol to achieve aweight of the entire solution of 100 g. To this solution, 2 g ofo-nitrobenzyl alcohol, a water generating agent, and 0.5 g of2-phenylsulfonylacetophenone [C₆ H₅ SO₂ CH₂ COC₆ H₅ ], an acidgenerating agent, were added and dissolved, to prepare a coatingsolution. With the use of this coating solution, coating and irradiationwith ultraviolet rays were conducted in the same manner as in Example 1.The amount of irradiated ultraviolet rays was 700 mJ/cm². Afterirradiation of ultraviolet rays and drying, the film was immersed in2-methoxyethanol for one minute for development. Thereafter, the filmwas immersed in IPA as a rinsing solution, and sintered in the samemanner as in Example 1 to obtain a satisfactory negative-type patterncomprising an oxide thin film (PZT thin film) having a thickness ofabout 600 Å. Perovskite-type PZT was confirmed through an X-raydiffraction analysis.

Even when the ultraviolet ray source was replaced with a KrF laser, orwhen the solvent for development was replaced with a mixed solvent of2-methoxyethanol and IPA, similar negative-type patterns were obtained.

Comparative Example 2

Formation of a PZT thin film pattern was attempted in the same manner asin Example 4, except that neither o-nitrobenzyl alcohol (as a watergenerating agent) nor 2-phenylsulfonylacetophenone (as an acidgenerating agent) was added to the composition. After irradiation withultraviolet rays, there was almost no difference in solubility betweenthe exposed and the non-exposed portions, and immersion in a solvent fordevelopment (water, or 2-methoxyethanol, or a mixed solvent of2-methoxyethanol and IPA) after drying by heating did not permitselective dissolution and removal of the non-exposed portion.

EXAMPLE 18

A composition for forming a metal oxide film pattern (coating solution)was prepared in the same manner as in Example 1, except that 2.9 g of2-nitroethanol (C₂ H₅ NO₃) were added as the water generating agent. Theatomic ratio of the individual metals contained in the coating solutionwas Pb:Zr:Ti=1:0.52:0.48.

This coating solution was applied onto a platinum substrate in the samemanner as in Example 1, and irradiation with far-ultraviolet rays,etching, rinsing and sintering were carried out also in the same manneras in Example 1. The amount of irradiation was 1,200 mJ/cm².

The resultant PZT thin film was confirmed to have a perovskite-typestructure through X-ray diffraction and through EPMA and XPS analysis tohave a composition: PbZr₀.52 Ti₀.48 O₃. The thin film obtained had asatisfactory thin film pattern.

When a KrF excimer laser generating a single wavelength of 249 nm wasused as an ultraviolet-ray source, a similar result was obtained. Inthis example, a satisfactory negative-type PZT thin film pattern couldbe formed with an ultraviolet-ray irradiation energy of at least 100mJ/cm (or more preferably, at least 500 mJ/cm²).

A similar satisfactory negative-type pattern was obtained even when thesolvent used for development was replaced with a mixed solution of2-methoxyethanol and IPA (mixing ratio in volume: 1:1).

EXAMPLES 19 TO 26

PZT thin films were formed in the same manner as in Example 18, exceptthat the water generating agents as shown in Table 2 were used and theamounts of irradiated ultraviolet rays, the etching liquids and theetching times as shown in Table 2 were used. As a result, satisfactorythin film patterns were obtained in all cases. These thin films had aperovskite structure, and were confirmed to have a composition:

    PbZr.sub.0.52 Ti.sub.0.48 O.sub.3.

                                      TABLE 2                                     __________________________________________________________________________                     Amount of                                                                     irradiated           Etching                                 Example                                                                            Water generating                                                                          ultraviolet                                                                           Etching      time                                    No.  agent       rays (mJ/cm.sup.2)                                                                    liquid       (min)                                   __________________________________________________________________________    19   2-nitroethanol                                                                            1200    2-methoxyethanol                                                                           1                                       20   Formaldehyde                                                                              1000    2-methoxyethanol + IPA                                                                     1                                       21   Tartaric acid                                                                             1100    2-methoxyethanol + IPA                                                                     1                                       22   2-hydroxybenzyl alcohol                                                                    900    2-methoxyethanol                                                                           5                                       23   2-carboxybenzyl alcohol                                                                    900    2-methoxyethanol + IPA                                                                     5                                       24   2-carboxybenzaldehyde                                                                      900    2-methoxyethanol                                                                           5                                       25   2-nitrobenzaldehyde                                                                        900    2-methoxyethanol                                                                           5                                       26   Phthalic acid                                                                             1100    2-methoxyethanol + IPA                                                                     3                                       __________________________________________________________________________     IPA: Isopropyl alcohol (mixing volume ratio with.2 methoxyethanol:1:1)   

Comparative Example 3

Formation of a PZT thin film pattern was attempted in the same manner asin Example 18, except that 2-nitroethanol, as a water generating agent,was not added to the composition. There was almost no difference insolubility between the exposed and the non-exposed portions afterirradiation with ultraviolet rays, and even when development wasattempted with water or 2-methoxyethanol, or a mixed solvent of2-methoxyethanol and IPA, after heating to dry, the non-exposed portioncould not selectively be removed.

EXAMPLES 27 TO 40

Solutions comprising the hydrolytic metal compounds and solvents shownin Table 3 were prepared in the same manner as in Example 18. (Whenusing two or more hydrolytic organic metal compounds, the mixing ratiowas set to match the stoichiometric ratio of the metals of the targetmetal oxides.) Coating solutions for forming an oxide thin film of thetarget chemical composition were prepared by adding, to these solutions,2-nitroethanol serving as a water generating agent in an amount of 2 wt.% relative to the solutions. With the use of each of these coatingsolutions, a metal oxide thin film was formed in the same manner as inExample 18. The coating had a thickness of about 600 Å in each case, andthe film was developed with 2-methoxyethanol and rinsed with n-hexane.In each case, a satisfactory thin film pattern comprising a metal oxideof the composition shown in Table 3 was obtained after sintering.

                                      TABLE 3                                     __________________________________________________________________________                       Composition for forming metal oxide thin film                   Composition of metal                             Concentration as        Example                                                                            oxide thin film (ratio                           converted into          No.  in ( ) represents mol ratio)                                                                Hydrolytic metal compound                                                                              Solvent   metal oxide             __________________________________________________________________________                                                          (%)                     27   PbTiO.sub.3   Pb(OCOCH.sub.3).sub.2, Ti(OCH(CH.sub.3).sub.2).sub.4                                                   2-methoxyethanol                                                                        10                      28   Pb.sub.0.91 La.sub.0.09 Zr.sub.0.65 Ti.sub.0.35 O.sub.3                                     Pb(OCOCH.sub.3).sub.2, La(OCOCH.sub.3).sub.3,                                                          2-methoxyethanol                                                                        10                                         Zr(O(CH.sub.2).sub.3 CH.sub.3).sub.4,                                         Ti(OCH(CH.sub.3).sub.2).sub.4                              29   Pb.sub.0.8 La.sub.0.2 TiO.sub.3                                                             Pb(OCOCH.sub.3).sub.2, La(OCOCH.sub.3).sub.3,                                 Ti(OCH(CH.sub.3).sub.2).sub.4                                                                          2-methoxyethanol                                                                        10                      30   SrTiO.sub.3   Sr(OCH.sub.2 CH.sub.3).sub.2, Ti(OCH(CH.sub.3).sub.2).s                       ub.4                     2-methoxyethanal                                                                        5                       31   Ba.sub.0.5 Sr.sub.0.5 TiO.sub.3                                                             Ba(OCH.sub.2 CH.sub.3).sub.2, Sr(OCH.sub.2 CH.sub.3).su                       b.2,                     2-methoxyethanol                                                                        5                                          Ti(OCH(CH.sub.3).sub.2).sub.4                              32   PbMg.sub.0.33 Nb.sub.0.67 O.sub.3                                                           Pb(OCOCH.sub.3).sub.2, Mg(OCH.sub.2 CH.sub.3).sub.2,                          Nb(OCH.sub.2 CH.sub.3).sub.5                                                                           2-methoxyethanal                                                                        10                      33   Bi.sub.4 Ti.sub.3 O.sub.12                                                                  BiO(OCOCH.sub.3), Ti(OCH(CH.sub.3).sub.2).sub.4                                                        Acetic acid                                                                             5                       34   ZnO--Al.sub.2 O.sub.3 (1:1)                                                                 Zn(OCH.sub.2 CH.sub.3).sub.2, Al(OCH(CH.sub.3).sub.2).s                       ub.3                     2-methoxyethanol                                                                        5                       35   SnO.sub.2 --Sb.sub.2 O.sub.3 (1:1)                                                          Sn(OC(CH.sub.3).sub.3).sub.4, Sb(O(CH.sub.2).sub.3                            CH.sub.3).sub.5          n-butanol 6                       36   In.sub.2 O.sub.3 --Sn.sub.2 O.sub.3 (1:1)                                                   In(OCH.sub.2 CH.sub.3).sub.3, Sn(OC(CH.sub.3).sub.3).su                       b.4                      n-butanol 5                       37   TiO.sub.2     Ti(OCH(CH.sub.3).sub.2).sub.4                                                                          2-methoxyethanol                                                                        5                       38   SiO.sub.2     Si(OCH.sub.2 CH.sub.3).sub.4                                                                           Isopropyl alcohol                                                                       5                       39   RuO.sub.2     RuCl.sub.4               Ethanol   5                       40   LiNbO.sub.3   Li(OCH.sub.2 CH.sub.3), Nb(OCH.sub.2 CH.sub.3).sub.5                                                   Ethanol   5                       __________________________________________________________________________

EXAMPLE 41

[Pb(CH₃ COO)₂.3H₂ O] in an amount of 11.84 g was dissolved in2-methoxyethanol serving as the solvent, and the resultant solution washeated to cause dehydration. [Zr(O(CH₂)₃ CH₃)₄ ] in an amount of 6.87 gand [Ti(OCH(CH₃)₂)₄ ] in an amount of 4.09 g were added to thissolution, and the solution was diluted with 2-methoxyethanol to achievea weight of the entire solution of 100 g. To this solution, 2 g of2-nitroethanol, a water generating agent, and 0.5 g of2-phenylsulfonylacetophenone [C₆ H₅ SO₂ CH₂ COC₆ H₅ ], an acidgenerating agent, were added and dissolved, to prepare a coatingsolution. With the use of this coating solution, coating and irradiationwith ultraviolet rays were conducted in the same manner as in Example18. The amount of irradiated ultraviolet rays was 700 mJ/cm². Afterirradiation and drying, the film was immersed in 2-methoxyethanol forone minute for development. Thereafter, the film was immersed in IPA asa rinsing solution, and sintered in the same manner as in Example 18 toobtain a satisfactory negative-type pattern comprising an oxide thinfilm (PZT thin film) having a thickness of about 600 Å. Perovskite-typePZT was confirmed through an X-ray diffraction analysis.

Even when the ultraviolet-ray source was replaced with a KrF laser, orwhen the solvent for development was replaced with a mixed solvent of2-methoxyethanol and IPA, similar negative-type patterns were obtained.

According to the present invention, as is clear from the resultspresented above, it is possible to form a negative-type metal oxide thinfilm pattern by using the sol-gel method and without using a resist. Itis therefore possible to simplify the device manufacturing process andimprove the efficiency thereof. Because of the utilization of thesol-gel method, a film can be formed at a lower cost more efficiently ascompared with a gas phase method such as CVD or sputtering, and a largerarea can easily be achieved, with almost no change in composition.

In the present invention, furthermore, a water generating agent ispresent in the coated film. This permits formation of a pattern with asmaller amount of irradiating energy, and the obtaining of a clearpattern by the use of an industrial ultraviolet-ray irradiatingapparatus. Since development can be accomplished with a relatively safeand inexpensive solution that is free from corrosive action such as analcohol, liquid waste treatment is simple.

The use of an acid generating agent, in combination with the watergenerating agent, makes it possible to form a pattern with an evensmaller irradiating energy.

What is claimed is:
 1. A composition for forming a metal oxide thin filmpattern, which comprises a solution containing one or more hydrolyticmetal compounds comprising hydrolytic organometallic compounds, aphotosensitizer which forms water under irradiation with active rays anda photosensitizer which forms an acid under irradiation with activerays, wherein said photosensitizer which forms an acid under irradiationwith active rays is 2-phenylsulfonyl acetophenone.
 2. A composition forforming a metal oxide thin film pattern as claimed in claim 1, whereinthe concentration of said hydrolytic metal compound in said compositionis within a range of from 1 to 20 wt. %, and the concentration of saidphotosensitizer which forms water under irradiation with active rays iswithin a range of from 0.001 to 20 wt. %.
 3. A composition for forming ametal oxide thin film pattern as claimed in claim 1, wherein theconcentration of said photosensitizer which forms an acid underirradiation with active rays in said composition is within a range offrom 0.001 to 20 wt. %, and the total concentration of saidphotosensitizer which forms water under active rays and saidphotosensitizer which forms an acid under irradiation with active raysis up to 20 wt. %.
 4. A composition for forming a metal oxide thin filmpattern, which comprises a solution containing a hydrolyticorganometallic compound and at least one photosensitizer which formswater under irradiation with active rays, said photosensitizer beingselected from the group consisting of 2-nitroethanol, formaldehyde,tartaric acid, 2-hydroxybenzyl alcohol, 2-carboxybenzyl alcohol,2-carboxybenzaldehyde, 2-nitrobenzaldehyde and phthalic acid.
 5. Acomposition for forming a metal oxide thin film pattern as claimed inclaim 4, wherein said solution further contains a photosensitizer whichforms an acid under irradiation with active rays.
 6. A composition forforming a metal oxide thin film pattern as claimed in claim 5, whereinsaid photosensitizer which forms an acid under active rays is2-phenylsulfonylacetophenone.
 7. A composition for forming a metal oxidethin film pattern as claimed in claim 4, wherein the concentration ofsaid hydrolytic metal compound in the composition is within a range offrom 1 to 20 wt. %, and the concentration of said photosensitizer whichforms water under irradiation of active rays is within a range of from0.001 to 20 wt. %.
 8. A composition for forming a metal oxide thin filmpattern as claimed in claim 5, wherein the concentration of saidphotosensitizer which forms an acid under irradiation with active raysin the composition is within a range of from 0.001 to 20 wt. %, and thetotal concentration of said photosensitizer which forms water underirradiation with active rays and said photosensitizer which forms anacid under irradiation with active rays is up to 20 wt. %.
 9. Acomposition for forming a metal oxide thin film pattern, which comprisesa solution containing one or more hydrolytic metal compounds comprisingmetal halides, and a photosensitizer which forms water under irradiationwith active rays; andwherein said metal halides coexisting with saidphotosensitizer are converted into the metal oxide under irradiationwith active rays, followed by heat treatment, wherein saidphotosensitizer which forms water under irradiation with active rays isat least one compound selected from the group consisting ofo-nitrobenzyl alcohol and 1-hydroxymethyl-2-nitronaphthalene.
 10. Acomposition for forming a metal oxide thin film pattern as claimed inclaim 9, wherein the concentration of said hydrolytic metal compound insaid composition is within a range of from 1 to 20 wt. % and theconcentration of said photosensitizer which forms water underirradiation with active rays is within a range of from 0.001 to 20 wt.%.
 11. A composition for forming a metal oxide thin film pattern,whichcomprises a solution containing one or more hydrolytic metal compoundscomprising metal halides, a photosensitizer which forms water underirradiation with active rays, and a photosensitizer which forms an acidunder irradiation with active rays; and wherein said metal halidescoexisting with said photosensitizers are converted into the metal oxideunder irradiation with active rays, followed by heat treatment, whereinsaid photosensitizer which forms an acid under irradiation with activerays is 2-phenyl-sulfonylacetophenone.
 12. A composition for forming ametal oxide thin film pattern as claimed in claim 11, wherein theconcentration of said hydrolytic metal compound in said composition iswithin a range of from 1 to 20 wt. %, and the concentration of saidphotosensitizer which forms water under irradiation with active rays iswithin a range of from 0.001 to 20 wt. %.
 13. A composition for forminga metal oxide thin film pattern as claimed in claim 11, wherein theconcentration of said photosensitizer which forms an acid underirradiation with active rays in said composition is within a range offrom 0.001 to 20 wt. %, and the total concentration of saidphotosensitizer which forms water under irradiation with active rays andsaid photosensitizer which forms an acid under irradiation with activerays is up to 20 wt. %.
 14. A composition for forming a metal oxide thinfilm pattern, which comprises a solution containing a hydrolytic metalcompound comprising a metal halide and one or more compounds selectedfrom the group consisting of 2-nitroethanol, formaldehyde, tartaricacid, 2-hydroxybenzyl alcohol, 2-carboxybenzylalcohol,2-carboxybenzaldehyde, 2-nitrobenzaldehyde and phthalic acid, saidsolution also containing a photosensitizer which forms an acid underirradiation with active rays,wherein said photosensitizer which forms anacid under irradiation with active rays is2-phenyl-sulfonylacetophenone.
 15. A composition for forming a metaloxide thin film pattern as claimed in claim 14, wherein theconcentration of said hydrolytic metal compound in the composition iswithin a range of from 1 to 20 wt. %, and the concentration of saidphotosensitizer which forms water under irradiation with active rays iswithin a range of from 0.001 to 20 wt. %.
 16. A composition for forminga metal oxide thin film pattern as claimed in claim 14, wherein theconcentration of said photosensitizer which forms an acid underirradiation with active rays in the composition is within a range offrom 0.001 to 20 wt. %, and the total concentration of saidphotosensitizer which forms water under irradiation with active rays andsaid photosensitizer which forms an acid under irradiation with activerays is up to 20 wt. %.